A display panel having an electrooptical substance sealed between a first substrate and a second substrate with a plate surface larger in area than a plate surface of the first substrate is known as a display means that displays an image according to an electric signal. The electrooptical substance is a substance whose optical characteristics, such as transmittance and luminance, change depending on electric signals (current signals or voltage signals) supplied to the substance. Examples of such a substance include liquid crystal and organic EL material. The second substrate has a substrate overlapping area defined such that the substrate overlapping area overlaps the first substrate in a plan view, and a substrate non-overlapping area defined such that, with one side edge of the second substrate extending out from one side edge of the first substrate, the substrate non-overlapping area does not overlap the first substrate. In an image display area in the substrate overlapping area, an electric signal is supplied to the electrooptical substance disposed in the image display area, and an image that can be read from the outer surface side of the first substrate is displayed. In the substrate non-overlapping area, electronic components or the like for supplying electric signals are mounted by a chip-on-glass (COG) method, and a terminal pad, to which a transmission component or the like for transmitting electric signals is connected, is formed. In the substrate non-overlapping area, an information code describing information for management of substrate production/inspection history may also be provided.
In recent years, the display panel has been modified in shape to give it a special form and reduced in frame size, which has led to a reduction in the area of the substrate non-overlapping area. To deal with this trend, efforts are being made to reduce the size of the terminal pad and information code. At the same time, a technology for placing the terminal pad and information code on the substrate in a space-saving manner is in demand.
According to Patent Document 1, an identification symbol (equivalent to the information code) that can be read from the back surface side of a display panel, i.e., the outer surface side of an array substrate (equivalent to the second substrate) is disposed at a location overlapping an inter-substrate conduction area, where the array substrate is electrically connected to a counter substrate (equivalent to the first substrate) via an inter-substrate conductive material, in a plan view. This technology provides a configuration that secures an identification symbol formation area while dealing with a reduction in the frame size of the display panel.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-255853
According to the above liquid crystal display device, the identification symbol is disposed overlappingly on the back surface side of an element (inter-substrate conductive material) having a specific function in the display panel to offer a space-saving effect. However, a transmissive liquid crystal display device of an ordinary structure has a backlight unit attached to the outer surface side of the array substrate, i.e., back surface side of the display panel. Because of this configuration, to read an identification symbol pattern from the back surface side of the display panel after the display device is completed, the backlight unit must be removed. Meanwhile, the counter substrate has a nontransparent shading layer (black matrix (BM) layer) disposed at a location overlapping the inter-substrate conduction area in a plan view. To read the identification symbol pattern from the front surface side (image display surface side) of the display panel, therefore, an opening must be created on the shading layer. Such an opening, however, raises a concern that light may leak from the opening. For the above reasons, after the liquid crystal display device is completed, the identification symbol pattern cannot be read easily from both front surface side and back surface side.